Physicochemical and antibacterial properties of lactoferrin and its hydrolysate produced by heat treatment at acidic pH.

In order to apply functionally active lactoferrin (Lf) to food products, the effect of pH on the heat stability of Lf was studied. Lf was easily denatured to an insoluble state by heat treatment under neutral or alkaline conditions, above pH 6. In contrast, it remained soluble after heat treatment under acidic conditions at pH 2 to 5, and the HPLC pattern of Lf heat-treated at pH 4 at 100 degrees C for 5 min was the same as that of native Lf. Lf was found to be very thermostable at pH 4, and could be pasteurized or sterilized without any significant loss of its physicochemical properties. Lf was hydrolyzed by heat treatment at pH 2 to 3 at above 100 degrees C, and its iron binding capacity and antigenicity were lost. But the antibacterial activity of the hydrolysate was found to be much stronger than that of native Lf. The antibacterial component of Lf hydrolysate produced by heat treatment at acidic pH was verified to be a peptide including the sequence of residues 1-54 from the N-terminal end of the bovine Lf molecule.